1. Field of the Invention
This invention relates to mechanical self-reciprocating oscillators and mechanisms and methods for establishing and maintaining regular back and forth movement of a micromachined device without the aid of any electronic components.
2. Background Art
The following are related to the invention and may be referenced herein:                [1] W. Tang et al., “Electrostatic Comb-Drive of Lateral Polysilicon Resonators,” SENSORS AND ACTUATORS A (PHYSICAL), v A21, n 1-3, February 1990, pp. 328-31.        [2] S. Zeng et al., “Fabrication and Characterization of Electrokinetic Micro Pumps,” THERMOMECHANICAL PHENOMENA IN ELECTRONIC SYSTEMS, v 2, 2000, pp. 31-36.        [3] C. Wilson et al., “Spectral Detection of Metal Contaminants in Water Using an On-Chip Microglow Discharge,” IEEE TRANS. ELECTRON DEVICES, v 49, n 12, December 2002, pp. 2317-22.        [4] J. Lee et al., “A Miniaturized High-Voltage Solar Cell Array as an Electrostatic MEMS Power Supply,” J. MEMS, v 4, September 1995, pp. 102-108.        [5] J. Bates et al., “Rechargeable Solid State Lithium Microbatteries,” IEEE MEMS, 1993, pp. 82-86.        [6] H. Jiang et al., “On-Chip Integration of High-Voltage Generator Circuits for an Electrostatic Micromotor,” INTL. CONF. ON SOLID-STATE SENSORS AND ACTUATORS, v 1, 1995, pp. 150-53.        [7] C. Ahn et al., “A Comparison of Two Micromachined Inductors (Bar and Meander-Type) for Fully Integrated Boost DC/DC Power Converters,” IEEE TRANSACTIONS ON POWER ELECTRONICS, v 11, n 2, March 1996, pp. 239-45.        [8] G. Skidmore et al., “Assembly Technology Across Multiple Length Scales From the Micro-Scale to the Nano-Scale,” IEEE MEMS, 2004, pp. 588-92.        [9] H. Armagnat, THE THEORY, DESIGN AND CONSTRUCTION OF INDUCTION COILS, New York, McGraw Publishing Company, 1908.        [10] R. Jaeger, MICROELECTRONIC CIRCUIT DESIGN, McGraw-Hill, 1997.        [11] K. Udeshi et al., “A DC-Powered, Tunable, Fully Mechanical Oscillator Using In-Plane Electrothermal Actuation,” IEEE MEMS, 2004, pp. 502-06.        [12] N. Mohan et al., POWER ELECTRONICS: CONVERTERS, APPLICATIONS, AND DESIGN, New York, John Wiley & Sons, Inc., 1995.        [13] W. Flanagan, HANDBOOK OF TRANSFORMER DESIGN AND APPLICATIONS, McGraw-Hill, Inc., 1993.        [14] H. Lorents et al., “SU-8: A Low Cost Negative Resist for MEMS,” J. MICROMECH. MICROENG, v 7, n 3, 1997, pp. 121-24.        [15] J. Stewart et al., THEORY AND DESIGN OF CAPACITOR-STORAGE IGNITION SYSTEMS, Technical Report, University of Michigan, Ann Arbor, 1956.        
A large number of micromachined devices ranging from electrostatic actuators [1], to microfluidic electrokinetic pumps [2], to microplasmas [3], all need high voltages for their operation. This requirement for high voltages is what prevents the use of these devices in integrated Microsystems and portable devices as they can only be powered by a single low-voltage DC supply. The need for high voltage generators extends to automotive transducers and a variety of portable electronic devices that use LCD display technology. In order to meet this demand, schemes have been proposed to integrate an additional miniaturized high voltage power source [4,5]. These, however, occupy large footprints and entail the additional overhead of power management and distribution. The preferred solution is to step up voltage from the low voltage DC power source such as a battery. A typical implementation of such a high voltage generator utilizes an inductor in conjunction with a switch that periodically breaks the current through the inductor. The miniaturization and integration of this high voltage generator has been limited by the need for an efficient inductive element as well as a high power, high voltage switch.
Traditionally, microelectronic transistors have been used as switches for high voltage generators. However, in standard CMOS technology transistors are severely limited by their dielectric and junction breakdown voltages, making them unsuitable for any application that demands even moderately high voltage or power levels [6]. The use of hybrid high voltage CMOS technology results in increased costs, and yet can handle only voltages up to about 80 V. In addition to the voltage limitation, transistors need electrical control signals that determine their switching characteristics. These control signals are generally obtained from an oscillator. The inductive element may be microfabricated, but typically results in modest inductance values [7]. An alternative approach is to integrate wire wound inductors using microassembly techniques [8].
The following are also related to the invention and may be referenced herein:                [A] D. Burns et al., “Sealed-Cavity Resonant Microbeam Pressure Sensor,” SENSORS AND ACTUATORS, A: PHYSICAL, v 48, n 3, May 30, 1995, pp. 179-86.        [B] T. Roessig et al., “Surface-Micromachined Resonant Accelerometer,” INTERNATIONAL CONFERENCE ON SOLID-STATE SENSORS & ACTUATORS, PROC., v 2, 1997, pp. 859-62.        [C] M. Putty et al., “A Micromachined Vibrating Ring Gyroscope,” SOLID-STATE SENSOR & ACT. WORKSHOP, 1994, pp. 213-20.        [D] C. Nguyen, “High-Q Micromechanical Oscillators and Filters for Communications,” 1997 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS, 1997, pp. 2825-28.        [E] A. Dec et al., “Microwave MEMS-Based Voltage-Controlled Oscillators,” IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, v 48, n 11, November 2000, pp. 1943-49.        [F] L. Que et al., “Bent-Beam Electro-Thermal Actuators for High Force Applications,” IEEE INTERNATIONAL MEMS, 1999, pp. 31-36.        [G] B. Jensen et al., “Design Optimization of a Fully-Compliant Bistable Micro-Mechanism,” ASME INTERNATIONAL MECHANICAL ENGINEERING CONGRESS AND EXPOSITION, 2001, pp. 357-63.        [H] L. Chu, FEEDBACK CONTROLLABLE ID AND 2D MICRO POSITIONERS USING ELECTROTHERMAL ACTUATORS AND CAPACITIVE DISPLACEMENT SENSORS, Ph.D. Dissertation, Univ. of Wisconsin-Madison, 2003.        [I] H. Lorents et al., “SU-8: A Low-Cost Negative Resist for MEMS,” J. MICROMECH. MICROENG. 7, 1997, pp. 121-24.        [J] J. Park et al., “Long Throw and Rotary Output Electro-Thermal Actuators Based on Bent-Beam Suspensions,” PROCEEDINGS OF THE IEEE MICRO ELECTRO MECHANICAL SYSTEMS (MEMS), 2000, PP. 680-85.        
Oscillators generate a modulating signal from a DC power source and are used in all applications that require periodic excitation. A wide spectrum of micromachined devices ranging from strain and pressure sensors [A] to accelerometers and gyroscopes [B,C] either require or exhibit improved performance when driven by a modulating signal.
On-chip signal generators reported in the past needed electronic components for their operation. The implementation of these oscillators using standard microelectronic circuits severely limits their voltage and power handling capacity and makes them unsuitable for direct use in any application demanding even moderately high voltages or power levels. Even oscillators that have utilized MEMS components have all used electronics to provide feedback of an amplified signal. Micromachined mass-spring systems have been used to replace LC tank circuits to provide frequency selective feedback [D]. In other cases, MEMS-based variable capacitors have been used to make voltage controlled tunable oscillators [E].
U.S. Pat. No. 6,594,994 discloses a micromechanical electrothermal actuator formed on a substrate.